The differences of axial length measurements between A-scan ultrasound and partial coherence interferometry (IOL Master) in macula-off retinal detachment

Abstract

The purpose of this study is to compare the axial length measurement by A-scan ultrasound and partial coherence interferometery (IOL Master) in eyes with macula-off retinal detachment. This study is a retrospective medical record review of 46 patients who had macula-off retinal detachment with contralateral normal eye from August 1, 2009, to August 31, 2011. The axial length measured by A-scan ultrasound and IOL Master was compared with paired t test. Correlation between 2 methods was assessed by Pearson correlation coefficient and agreement between 2 methods was analyzed by Bland-Altman plot.The mean axial length was 25.07 ± 1.85 mm by A-scan ultrasound and 25.14 ± 1.87 mm by IOL Master in normal eyes group and 24.91 ± 1.80 mm by A-scan ultrasound and 24.03 ± 2.00 mm by IOL Master in detached eyes group, respectively. The mean axial length by A-scan ultrasound was shorter in normal eyes group but longer in the detached eyes group than that by IOL Master. The axial length measured by 2 methods was strongly correlated in normal and detached eyes groups. There were close ranges of 95% limits of agreement in normal eyes group and wide ranges of 95% limits of agreement in the detached eyes group in Bland-Altman plot. The intraocular lens (IOL) power in normal eyes group was 16.96 ± 5.25 D by A-scan ultrasound and 17.22 ± 5.33 D by IOL Master and the difference between 2 methods was not significantly different. However, the IOL power in detached eye groups was 17.34 ± 4.81 D by A-scan ultrasound and 19.90 ± 5.27 D by IOL Master and the difference of IOL power was clinically significantly different. The axial length by IOL Master was shorter and IOL power by IOL Master was stronger than those measured by A-scan ultrasound in macula-off retinal detachment. IOL Master would detect the detached retina rather than the retinal pigment epithelium. This implies that axial length and IOL power calculated by A-scan would be more appropriate than those by IOL Master.